Components such as combustor-to-turbine transition ducts that are in combustion gas flow areas of gas turbines require cooling to maintain design temperatures. Cooling efficiency is important in order to minimize the usage of air diverted from the compressor for cooling. Impingement cooling is a technique in which a perforated wall is spaced from a hot wall to be cooled. Cooling air flows through the perforations and forms jets that impinge on the hot wall. However, the impinged air then flows across the wall surface, interfering with other impingement jets. This is called “cross-flow interference” herein. Other cooling techniques use elements such as cooling channels, fins, and pins to provide increased surface area for convective/conductive heat transfer. However, the coolant becomes warmer with distance, reducing uniformity of cooling. Film cooling provides an insulating film of cooling air on a hot gas flow surface via holes through the wall from a coolant supply. This can be effective, but uses a high amount of coolant.
Combinations of cooling techniques have been used, as exemplified by US Patent Application Publication No. US 2008/0276619 A1, which teaches a cooling channel having a plurality of impingement jet inlets and a plurality of outlets. However, as the combustion temperatures in advanced turbine designs continue to increase, there is an ongoing need for improved cooling arrangements.